Why did President Grover Cleveland refuse to annex Hawaii during his terms?

In the first year of his second term (1893-97), President Grover Cleveland said: "I conceived it to be my duty therefore to withdraw the treaty from the Senate for examination, and meanwhile to cause an accurate, full, and impartial investigation to be made of the facts attending the subversion of the constitutional Government of Hawaii and the installment in its place of the provisional government."
This was Cleveland's response to the recent American-led coup against the government of Hawaii. That coup led to the overthrow of Queen Liliukalani in January 1893. Cleveland was not happy with American involvement in the coup, so he was not willing to admit Hawaii as a state. In addition, he called for the restoration of the Queen to her throne.
Prior to the plot of 1893, American influence in Hawaii had grown steadily. There were religious, military, and economic reasons for America's interest in Hawaii. American missionaries had been active in Hawaii for years. The U.S. Navy established a base there in 1887. American sugar planters had become increasingly active in the economy and politics of Hawaii in the years before the coup.
Sanford Dole (1844–1926), leader of the coup plotters, refused Cleveland's request to restore the Queen to power. Instead, he and his supporters established the Republic of Hawaii (1894). After Cleveland left office, Hawaii became a U.S. territory and, eventually, a state.
http://www.let.rug.nl/usa/documents/1876-1900/president-clevelands-message-about-hawaii-december-18-1893.php